The stratified squamous epithelium of mammalian esophagus actively transports sodium and chloride, thus creating the transmural electrical potential difference in this organ. The low rates of transport, plus the fact that electrolyte transport in this epithelium appears to be not altered by hormones such as cholecystokinin, gastrin, or secretin, or by neurohumoral agents such as carbachol and norepinephrine, support the concept that this epithelium has no significant role in water and electrolyte conservation. Rather, sodium transport in this epithelium might reflect cellular homeostasis, and thus the ability of the epithelium to act as a barrier between the outside world and the animal. The proposed work for the coming year will be to determine the effects of hydrogen ion on electrolyte transport in the in vitro esophageal epithelium. Transport of hydrogen ion, sodium, and chloride will be measured in the short-circuited, stratified squamous esophageal epithelium stripped of its muscle layers and placed in an Ussing chamber type apparatus. The effects of various mucosal hydrogen ion concentrations on ion transport, permeability and the electrical parameters will be determined. Synergistic effects of bile acids, alcohol, and salycilates with hydrogen ion will be sought. Correlation of transport studies with histology should give important insight, at the cellular level, into the pathophysiology of esophagitis.